1. Field of the Invention
The present invention relates generally to the fields of molecular biology and medicine. More particularly, it concerns imaging and the diagnosis and treatment of cancer.
2. Description of Related Art
In the United States, prostate cancer (PCa) has been the most commonly diagnosed cancer in males and is consistently among the leading causes of cancer-related deaths of men. According to the “2006 Cancer Facts and Figures” published by the American Cancer Society, an estimated 234,460 new cases of prostate cancer will be diagnosed and 27,350 men will die of prostate cancer in the United States alone in 2006. Most of the deaths from prostate cancer are related to advanced disease, in which patients present with bone metastasis and soft-tissue involvement. The risk of extraprostatic disease in patients with clinically localized disease typically remains high (30-60%), despite definite local therapy. The skeleton is the most common site for metastases in a variety of cancers, among which breast and prostate cancers account for over 80% of cases causing the great morbidity due to intractable bone pain, pathological fractures, hypercalcemia and nerve compression (Cole et al., 2000; Coleman, 2001). Once the tumor spreads to bone, it can become unresponsive to standard therapeutic treatments, and there is presently no effective treatment of bone metastases.
Whole-body bone scan using 99mTc-MDP (methylene diphosphonate) is currently the standard procedure for the detection of bone metastases after bone symptoms appear, although problems are associated with this approach. In clinical practice, the bone involvement may not be observed in the bone scan until 5 years after micrometastasis has occurred; therefore, a bone scan with negative results does not prove the absence of metastasis. Due to the limited specificity, 99mTc-MDP bone scan is often aided by other imaging modalities, such as X-ray radiography, MRI, CT, PET scans, and/or bone marrow biopsy for a final diagnosis. Thus, there exists a strong need to develop new agents that allow for the early diagnosis of the extraprostatic spread of PCa.